In many computers, a pointing device such as a mouse or a trackball is used to provide input (e.g., cursor control, screen scrolling, etc.). A typical computer mouse 1 is shown in FIG. 1. Mouse 1 has a case 2 having a bottom case 3 and an upper case 4. As a user slides mouse 1 across a planar (or substantially planar) surface, motion detectors and encoders within case 2 may convert the two-dimensional movement of the mouse across the surface into horizontal and vertical motion of a cursor, pointer, or other object on a computer screen. Mouse 1 has two buttons 5 and 6 which a user can “click” or “double click” to select something on a computer screen. Other mice may have fewer or additional buttons, or other features. Mouse 1 may be connected to a computer or other device by a cord 7 through which mouse 1 may receive power and communicate with a computer (or other device). Alternatively, mouse 1 could be battery powered and communicate via a wireless connection. Mouse 1 also has a scroll wheel 8. Scroll wheel 8 is located such that the mouse user can comfortably turn the scroll wheel with a finger. The mouse and/or computer may be configured such that turning the wheel causes the screen image to scroll upwards or downwards. Keyboards and other input devices may also include a scroll wheel or other control performing a similar function.
Recently, computer mice and keyboards including a horizontal scrolling control have been developed. For example, displayable portions of spreadsheets, large documents and various other images are often wider than the display screen. In order to view an entire image, the user must pan the display to one side. In the past, this has typically required selecting a horizontal scroll bar (or other graphical user interface on the display screen) with a mouse or other pointing device and then moving the mouse or other pointing device. Now, a horizontal scrolling control permits a user to pan a screen image by manipulating a wheel, a button or other type of control. Examples of horizontal scrolling controls are described in commonly-owned U.S. patent application Ser. No. 10/184,000 (titled “Input Device Including A Wheel Assembly for Scrolling An Image In Multiple Directions” and filed Jun. 28, 2002), Ser. No. 10/183,993 (titled “Input Device Including A Scroll Wheel Assembly for Manipulating An Image In Multiple Directions” and filed Jun. 28, 2002), Ser. No. 10/183,994 (titled “Scrolling Apparatus Providing Multi-Directional Movement of An Image” and filed Jun. 28, 2002) and Ser. No. 10/382,652 (titled “Scroll Wheel Assembly for Scrolling An Image In Multiple Directions” and filed Mar. 7, 2003), all of which are incorporated by reference herein.
One type of horizontal scrolling control is a scroll wheel which is also movable from side to side. When such a scroll wheel is moved in this fashion, the image displayed on a computer screen may be horizontally scrolled. Examples of such horizontal scroll wheels are described in the aforementioned Ser. Nos. 10/184,000 and 10/382,652 applications. Such a scroll wheel is a significant advancement. However, existing designs for this type of control typically include a number of parts. These parts must be separately manufactured and then assembled to form a functional device. Because of this, inclusion of a horizontal scroll feature in a mouse or other input device usually results in higher manufacturing costs. Significant cost advantages can be gained if the number of separate parts in a horizontal scroll mechanism can be reduced.